1. Field of the Invention
The present disclosure relates to power converters, and more particularly to multilevel inverters for converting direct current (DC) voltage into alternating current (AC) voltage.
2. Description of Related Art
Inverters convert DC voltage into AC voltage. Multilevel inverters employ multiple voltage levels and solid-state switch devices. The multiple voltage levels are generally formed by connections to a positive DC terminal, a negative DC terminal and a middle DC terminal having a potential greater than the negative DC terminal and less than the positive DC terminal. A controller cycles the solid-state switch devices between on and off states to generate output AC voltage, generally with a stepped waveform approximating a sinusoidal waveform. The solid-state switch devices are generally either insulated gate bipolar transistors (IGBTs) or field effect transistors (MOSFETs) grouped into one or more phase legs.
Each phase leg generally includes four serially connected solid-state switch devices. The outer of the serially connected devices connect directly to positive and negative DC terminals. The inner of the serially-connected devices are directly connected to one another, and indirectly connected to the positive and negative terminals through the outer devices. A middle DC lead typically connects indirectly through midpoint clamping devices to terminals located between each pair of inner and outer solid-state switch devices.
Such conventional methods and systems for power conversion have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved converters. The present disclosure provides a solution for this need.